As the number of interconnections on various types of electronic devices increases, the task of testing the quality of such interconnections becomes progressively more difficult. For example, pin grid arrays (PGAs), ball grid arrays (BGAs), chip scale packages (CSPs), and standard leaded components regularly employ well over one hundred interconnections, each of which is critical to the proper performance of the device. Additionally, probes for testing printed circuit boards, electronic components such as integrated circuits (ICs), and IC wafers must also be tested for quality prior to being employed in the test environment. Such probes may number in the thousands, further exacerbating the problems of testing such interconnections. As manual visual inspection of such interconnections and probes is necessarily slow and error-prone, automated systems have been devised to perform such inspection.
Currently, the quality of most IC interconnections is tested using structured or laser light. For example, structured light may be used to illuminate a single interconnection or a row of interconnections at an oblique angle, creating shadows of the interconnections. Given the expected size and shape of the interconnections and the angle of incident light, an expected shadow size and shape can be determined and compared to the actual shadow cast by the interconnection to determine the quality of the interconnection. Alternately, laser light can be projected substantially from the side of the connections so that opposing light detectors, by virtue of the laser light received, may be employed to determine if any interconnections are missing or are too short to be effective. Unfortunately, such systems generally require rather complex and expensive optics. Also, since these systems typically test one interconnection or row of interconnections at a time, inspection time per electronic device tends to be rather long. Additionally, the use of light-based inspection systems are susceptible to poor interconnections remaining undetected due to problems inherent in testing interconnections residing toward the center of an interconnection array by the use of structured light, due to the shadows cast by the surrounding interconnections.
From the foregoing, a new system and method of testing electronic device interconnections that requires no special optics, reduces the amount of testing time per device, and reduces the possibility of undetected interconnection defects would be advantageous.
Embodiments of the invention, to be discussed in detail below, provide a system and method for testing the quality of electronic device interconnections by way of a pressure-sensitive medium, such as, for example, a pressure-sensitive film. The interconnections of an electronic device are placed in contact with the pressure-sensitive medium, possibly by way of a robotic actuator. A mechanical force is then applied to the electronic device so that each interconnection of the electronic device exerts substantially identical pressure on the pressure-sensing medium, assuming no defects in the interconnections exist. As a result of the applied force, the pressure-sensitive means produces an indication of the pressure exerted by each interconnection. That indication is then analyzed, possibly by way of a camera and associated computer, to determine the quality of the interconnections.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.